I'm really interested in this. Have seen after market lamp conversions for the red reflectors located on rear of our CX-5, - the ones on each side, near tail pipes. My only feelings about the appearance of the back of the CX is that it is pretty plain, especially compared to some of the competitor's SUV's that have more, "jazzy," tail lights. Converting the lower reflectors to illuminated tail/brake/direction signal, Functional lights I would like. After market stuff, of course, is Chinese, so always suspect. I have seen some folks make these reflectors into rear fog lights, but that is not what I'm after.
Anyone doing this? I'd love to see what you've done and where you obtained parts, including wiring needed. (Will a trailer hitch harness from Mazda work?)

Our moderator Chris_Top_Her has done it on his gen-1 CX-5 not as the rear fog light, but brake and tail lights from some eBay Chinese LED unit. It should be easy, with some extra wire spliced into tail light and brake light wires.

Thanks. I'll watch for what Chris did - or look around for it.
I keep thinking it ought to be simple as well. Also, I need to look into what the trailer package harness has in it. That would break out all the lights I'm looking for and, if Mazda was thinking ahead, might be a plug in so I don't have to begin tapping or cutting into looms on our car that barely has 1,000 miles on it.

Thanks. I'll watch for what Chris did - or look around for it.
I keep thinking it ought to be simple as well. Also, I need to look into what the trailer package harness has in it. That would break out all the lights I'm looking for and, if Mazda was thinking ahead, might be a plug in so I don't have to begin tapping or cutting into looms on our car that barely has 1,000 miles on it.

If you turned your rear fog lights into aux lights, you would likely have to splice the power wire into your running light/brake light/flasher (however you want them to function)

Thanks. I am talking about the plain reflector non-illuminated lens, one on each side of the rear, bottom corners, near tail pipe. They are merely plastic reflectors now. I think they would help protect the rear if they could be converted into a second set of tail/brake/direction lights. Mirror the regular tail lights if you will. That's why I thought a trailer hitch harness would tap all that, but instead of hooking it up to trailer, hook it to new bottom lens units as long as they had bulb sockets, etc., Hope this makes sense.
Regular stock rear lights including any with fog capability, I do not want to change.

In theory, the trailer hitch harness and DIY retrofit of the lower reflectors should work just fine for what you plan to do. You could probably buy a pair of screw-on LED trailer brake lights and modify the socket and bulb assemblies to fit inside the reflectors.

Yes. Mounted as close to the ground as possible so it is visible sooner than tail lights

Here they are on a CX-5

That's Chris_Top_Her's mod I mentioned above!

Here show a visual example of on road usage.

Legally in Europe or other countries when Rear Fog Light is mandatory, you can only have one red bright tail light serving as rear fog light. It'd be on the left side for left-hand drive vehicles such as in Germany; but on the right side for right-had drive vehicles such as in UK. Or you can mount it in the middle, like on Mini, for any countries.

You need different light stalk switch with rear fog position which can only be toggled, so the rear fog has to be turned on manually again for each engine start-up to meet the regulation. The dash front and rear fog indicators are also required by law which are missing for our US CX-5.

Thanks. I am talking about the plain reflector non-illuminated lens, one on each side of the rear, bottom corners, near tail pipe. They are merely plastic reflectors now. I think they would help protect the rear if they could be converted into a second set of tail/brake/direction lights. Mirror the regular tail lights if you will. That's why I thought a trailer hitch harness would tap all that, but instead of hooking it up to trailer, hook it to new bottom lens units as long as they had bulb sockets, etc., Hope this makes sense.
Regular stock rear lights including any with fog capability, I do not want to change.

I was thinking about doing the exact same thing on my 17' CX-5, if you do go through with it, please post a write up.